Method and apparatus for manufacturing finned pipes

ABSTRACT

Cooling fins are rolled onto the outer surface of a pipe or tube, while simultaneously the cross section of the pipe or tube is changed to an oval or elliptical shape. The inner surface of the pipe or tube may be either smooth or provided with grooves. The fins are formed by three rotating dies, and the crosssectional shape and inner surface is formed by drawing the pipe or tube over a rotating mandrel.

United States Patent lnventor Appl. No. Filed Patented Assignee METHOD AND APPARATUS FOR MANUFACTURING FINNED PIPES 8 Claims, 15 Drawing Figs.

US. Cl 72/96,

72/100 Int. Cl.: 821d 19/08 Field of Search 72/77, 78,

[5 6] References Cited UNITED STATES PATENTS 1,909,005 5/1933 Paugh 29/1573 2,367,226 l/l945 Lonsdale... 72/96 2,430,210 11/1947 Bruegger 72/100 3,415,090 12/ 1968 Kirpichnikov et al. 72/100 FOREIGN PATENTS 111,528 9/1940 Australia 72/96 Primary ExaminerRichard J. l-lerbst Attorney-Spencer & Kaye ABSTRACT: Cooling fins are rolled onto the outer surface of a pipe or tube, while simultaneously the cross section of the pipe or tube is changed to an oval or elliptical shape. The inner surface of the pipe or tube may be either smooth or provided with grooves. The fins are formed by three rotating dies, and the cross-sectional shape and inner surface is formed by drawing the pipe or tube over a rotating mandrel.

Patented May 25, 1971 3,580,026

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5 Sheets-Sheet 3 Fl -4a Patented May 25, 1971 5 Sheets-Sheet 4 Patented May 25, 1971 3,580,026

5 Sheets-Sheet 5 METHOD AND APPARATUS FOR MANUFACTURING FINNED PIPES BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus which have cooling fins. The inside surface of the pipes are smooth, or are provided for producing oval or elliptical cross section pipes or tubes. Such pipes are made directly out of common round or oval pipes having smooth inside arid outside surfaces.

Rolled, finned pipes of oval or round cross section with a smooth or grooved inside surface, as well as their technical and economical advantages are well known. An advantage of particular importance is in utilization for the construction of heat exchangers.

Rolled finned pipes with or without inside grooves and having a circular cross section have the disadvantage that on assembling them in a bundle, the distance between two neighboring pipes in the same row is greater than with oval pipes. This also means that the outer liquid circulation through the bundles comes up against a higher resistance than it would with oval pipes.

Oval pipes with applied fins .have the disadvantages that they are more difficult to manufacture and have a lower heat transfer at the juncture than rolled, finned pipes. The latter have the advantage of unifonn contact of the fins with the base pipe. Of course, transfer coefficient depends also on the manufacture quality of the pipes! SUMMARY OF THE INVENTION The present invention eliminates these deficiencies by manufacturing the oval, finned pipes or tubes by a special rolling method. The fins are rolled directly out of the base pipe walls, and the pipes are ovalized concomitantly with the forming of the fins.

In this way, the fins are an integral part of the pipe itself, being rolled out of the pipe body, and have a good heat transfer coefficient. Besides, the setting of the pipes in bundles permits decreasing the distance between two pipes of the same row, and at the same time lowering the head resistance of the medium circulating outside the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view, partly in section, of the device according to the present invention.

FIG. 2a is a longitudinal view of one embodiment of a mandrel used to produce an oval pipe with a smooth inner surface.

FIG. 2b is a view similar to that of FIG. 2a of a second embodiment of a mandrel used for producing oval pipes with a smooth inner surface.

FIG. 3a is a cross-sectional view taken along the line 30-311 of FIG. 2a. I

FIG. 3b is a cross-sectional view taken along the line 3b-3b of FIG. 2b. 1

FIG. 4a is a longitudinal view of one embodiment of a mandrel used to produce oval pipes with inside grooves.

FIG. 4b is a view similar to that of FIG. 4a of a second embodiment of a mandrel used to make oval pipes with inside grooves.

FIG. 5a is a cross-sectional view taken along the line 5a-5a of FIG. 40.

FIG. 5b is a cross-sectional view taken along the line 5b-5b of FIG. 4b.

FIG. 6 is a longitudinal, cross-sectional view along the lines 6-6 of FIGS. 7a and 7b of a portion of an oval pipe with a smooth inside surface.

FIG. 7a is a cross-sectional view taken along line 7-7 of FIG. 6 showing one possible configuration of an oval pipe according to the present invention.

FIG. 7b is a cross sectional view taken along line 7-7 of FIG. 6 showing another possible configuration of an oval pipe according to the present invention.

FIG. 8 is a longitudinal, cross-sectional view taken along lines 8-8 of FIGS. 9a and 9b showing an oval pipe according to the present invention with a grooved inside surface.

FIG. 9a is a cross-sectional view taken along line 9-9 of FIG. 8 showing a possible configuration of an oval pipe according to the present invention with a grooved inside surface.

FIG. 9b is a cross-sectional view taken along line 9-9 of FIG. 8 showing another possible configuration of an oval pipe with a grooved inside surface according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 of the drawings, a pipe 5, which may be of circular or oval cross section, is pushed into a mandrel 1 by well known means. Mandrel I is rigidly fixed to a rotating rod 2. The rod 2, and hence the mandrel I, are supported in a well known manner so that they-are prohibited from moving axially. As the pipe or tube 5 is drawn over the mandrel 1, it also rotates with the mandrel.

Arranged around the mandrel l, in the manner shown in FIG. I, are three forming rolls 3 mounted on shafts 4. The three forming rolls 3 are rotated in the same direction about the shafts 4 by a common power source (not shown). As can be seen from FIG. 1, the periphery of each forming roll 3 is shaped like a threading die.

The mandrel 1 can have various cross-sectional shapes, depending on the configuration which it is desired to impart to the inner surface of the pipe. FIGS. 20 and 30 show one possible configuration of the mandrel 1 that will give the pipe a smooth inner surface; and FIGS. 2b and 3b show another mandrel configuration which will also give the pipe a smooth inner surface. FIGS. 6, 7a and 7b show pipes that have been formed by mandrels such as those of FIGS. 20 and 2b.

If it is desired to form oval pipes with grooved inner surfaces, FIGS. 4a and 5a show one mandrel configuration with a series of longitudinal channels. These channels may be either parallel to the axis of the mandrel, or of an angle to the axis so that the grooves in the pipe tend to spiral around the pipe, to form pipes with a grooved inner surface. FIGS. 4b and 5b also show a mandrel configuration to form pipes with a grooved inner surface. FIGS. 8, 9a and 9b show pipes that have been formed by mandrels such as those of FIGS. 4a and 4b.

The active zone of each of the mandrels 1, has a series of oval or elliptic sections which increase in cross-sectional area progressively until the mandrel reaches its maximum size, in the section constituting the calibrating zone, after which it has a bevelled or rounded end. The active zone of each mandrel for making grooved inner surfaces, contains the grooving channels.

Oval finned pipes or tubes according to the present invention are formed by the pipe or tube 5 being pushed in a well known manner between the three forming rolls 3 until the first fins are formed on the periphery of the pipe or tube 5. Once the rolls 3 have engaged the pipe or tube 5, the rolls 3 act to move it axially. At the same time, the pipe or tube 5 is rotating with the mandrel l. The calibrating zone of each of the three rolls 3 and the mandrel l coincide with each other so that as the pipe 5 moves axially it is deformed by both the rotating forming rolls 3 and the mandrel 1. In this manner, smooth surface pipes can be made into oval finned pipes.

It can be readily seen that the ovalized finned pipes of the present invention reduce heat exchanger sizes and, implicitly, the heat exchanger cost.

Iclaim:

l. A method for producing oval finned pipes or tubes, comprising the steps of: I

a. moving a pipe having smooth inner and outer surfaces over a rotating ovaling mandrel in rotating engagement therewith; and

b. rolling fins on the outer surface of the pipe while it is being moved over said mandrel.

2. Apparatus for producing oval finned pipes and tubes from smooth walled pipes and tubes comprising, in combination:

a. an axially fixed, rotating mandrel means over which a smooth walled pipe is drawn while being rotated with said mandrel means, said mandrel means being shaped to give the inner surface of said pipe its desired cross section; and

b. rotating die means disposed so as to roll integral fins on the outer surface of the pipe while it is drawing the pipe over said mandrel means.

3. The apparatus as defined in claim 2 wherein said rotating die means includes three forming rolls rotating in the same direction, each of said forming rolls having a die element on its periphery.

4. The apparatus as defined in claim 3 wherein said mandrel has a cross-sectional shape which varies along its length so that the pipe is progressively shaped as it is drawn over said mandrel.

5. The apparatus as defined in claim 4 wherein said mandrel has a smooth outer surface.

6. The apparatus as defined in claim 4, wherein said mandrel has a grooved outer surface.

7. The apparatus as defined in claim 6 wherein said grooves are parallel to the axis of the pipe.

8. The apparatus as defined in claim 6 wherein said grooves are at an angle relative to the axis of the pipe, so that the grooves formed in the pipe wind around the axis of the pipe. 

1. A method for producing oval finned pipes or tubes, comprising the steps of: a. moving a pipe having smooth inner and outer surfaces over a rotating ovaling mandrel in rotating engagement therewith; and b. rolling fins on the outer surface of the pipe while it is being moved over said mandrel.
 2. Apparatus for producing oval finned pipes and tubes from smooth walled pipes and tubes comprising, in combination: a. an axially fixed, rotating mandrel means over which a smooth walled pipe is drawn while being rotated with said mandrel means, said mandrel means being shaped to give the inner surface of said pipe its desired cross section; and b. rotating die means disposed so as to roll integral fins on the outer surface of the pipe while it is drawing the pipe over said mandrel means.
 3. The apparatus as defined in claim 2 wherein said rotating die means includes three forming rolls rotating in the same direction, each of said forming rolls having a die element on its periphery.
 4. The apparatus as defined in claim 3 wherein said mandrel has a cross-sectional shape which varies along its length so that the pipe is progressively shaped as it is drawn over said mandrel.
 5. The apparatus as defined in claim 4 wherein said mandrel has a smooth outer surface.
 6. The apparatus as defined in claim 4, wherein said mandrel has a grooved outer surface.
 7. The apparatus as defined in claim 6 wherein said grooves are parallel to the axis of the pipe.
 8. The apparatus as defined in claim 6 wherein said grooves are at an angle relative to the axis of the pipe, so that the grooves formed in the pipe wind around the axis of the pipe. 